Turkey's government has told U.S. officials it has audio and video proof that missing Saudi Arabian writer Jamal Khashoggi was killed and dismembered in the Saudi consulate in Istanbul, the Washington Post reported Friday.

The newspaper, for which Khashoggi is a columnist, cited anonymous U.S. and Turkish officials as saying the recordings show a Saudi security team detained the writer when he went to the consulate on Oct. 2 to pick up a document for his upcoming wedding.

According to the WP, the audio recording, in particular, provides some of the most persuasive and gruesome evidence that the Saudi team is responsible for Khashoggi’s death, the officials said.

“The voice recording from inside the embassy lays out what happened to Jamal after he entered,” said one person with knowledge of the recording who, like others, spoke on the condition of anonymity to discuss highly sensitive intelligence.

“You can hear his voice and the voices of men speaking Arabic,” this person said. “You can hear how he was interrogated, tortured and then murdered.”

A second person briefed on the recording said men could be heard beating Khashoggi.

Officers were looking into sound recordings sent from a smartwatch that Khashoggi was wearing when he was inside the consulate to a mobile phone which he gave to his Turkish fiancee waiting outside, Hatice Cengiz.

Khashoggi, who was considered close to the Saudi royal family, had become a critic of Crown Prince Mohammed bin Salman. Khashoggi, a former newspaper editor in Saudi Arabia, left the country last year. He advised Prince Turki al-Faisal, former Saudi intelligence chief, and has also been close to billionaire investor Prince Alwaleed bin Talal.

A delegation from Saudi Arabia arrived in Turkey Friday as part of an investigation into the writer's disappearance, Turkey's state-run news agency Anadolu said.

Saudi Arabia has called the allegation it abducted or harmed Khashoggi "baseless." However, it has offered no evidence to support its claim he left the consulate and vanished despite his fiance waiting outside.

Anadolu Agency said the delegation would hold talks with Turkish officials over the weekend. It did not provide further details.

On Thursday, Turkish presidential spokesman Ibrahim Kalın said Turkey and Saudi Arabia would form a "joint working group" to look into Khashoggi's disappearance.